Journal Article

Carbonation and decarbonation reactions; implications for planetary habitability

Schiffries, Craig M, Tao Renbiao, Tao Renbiao, Planavsky, Noah J, Stewart, Emily M, Isson, Terry T, Ague, Jay J, Ferry, John M

2019

Overview

The geologic carbon cycle plays a fundamental role in controlling Earth's climate and habitability. For billions of years, stabilizing feedbacks inherent in the cycle have maintained a surface environment that could sustain life. Carbonation/decarbonation reactions are the primary mechanisms for transferring carbon between the solid Earth and the ocean-atmosphere system. These processes can be broadly represented by the reaction: CaSiO3(wollastonite) + CO2(gas)⇌CaCO3(calcite) + SiO2(quartz). This class of reactions is therefore critical to Earth's past and future habitability. Here, we summarize their significance as part of the Deep Carbon Observatory's \"Earth in Five Reactions\" project. In the forward direction, carbonation reactions like the one above describe silicate weathering and carbonate formation on Earth's surface. Recent work aims to resolve the balance between silicate weathering in terrestrial and marine settings both in the modern Earth system and through Earth's history. Rocks may also undergo carbonation reactions at high temperatures in the ultramafic mantle wedge of a subduction zone or during retrograde regional metamorphism. In the reverse direction, the reaction above represents various prograde metamorphic decarbonation processes that can occur in continental collisions, rift zones, subduction zones, and in aureoles around magmatic systems. We summarize the fluxes and uncertainties of major carbonation/decarbonation reactions and review the key feedback mechanisms that are likely to have stabilized atmospheric CO2 levels. Future work on planetary habitability and Earth's past and future climate will rely on an enhanced understanding of the long-term carbon cycle.

• Publisher: Mineralogical Society of America,Walter de Gruyter GmbH
• Subject: atmosphere / Calcite / Calcium carbonate / Carbon / Carbon cycle / Carbon dioxide / carbon flux / Carbonates / Carbonation / carbonatization / chain silicates / chemical reactions / Climate / core / Decarbonation / Direction / Earth / Earth in Five Reactions: A Deep Carbon Perspective / Earth surface / Fluxes / framework silicates / geochemical cycle / Geochemistry / Habitability / High temperature / mantle / Metamorphism / Metamorphism (geology) / planetary interiors / planets / plate collision / plate tectonics / Quartz / Rift zones / Silica / silica minerals / Silicates / Silicon dioxide / Stabilizing / Subduction / Subduction (geology) / Subduction zones / theoretical studies / Urey reaction / Weathering / Wollastonite / wollastonite group / world ocean